Alpha decay is a type of radioactive decay in which an unstable nucleus emits an alpha particle, which is composed of two protons and two neutrons—identical to a helium-4 nucleus.
Key Features:
- The emission of an alpha particle causes the atomic number to decrease by 2 and the mass number to decrease by 4.
- This process transforms the original element into a new element, located two places earlier in the periodic table.
- Alpha decay typically occurs in heavy, unstable nuclei, such as uranium, radium, or thorium.
Why It Happens:
- Large nuclei have strong electrostatic repulsion between protons.
- Emitting an alpha particle helps reduce both mass and internal repulsion, moving the nucleus toward greater stability.
- Alpha particles are tightly bound and carry away significant energy, making this a favorable decay mode for some heavy elements.
Properties of Alpha Particles:
- They are highly ionizing but have low penetration power, easily stopped by a sheet of paper or human skin.
- Their short range makes them dangerous only if ingested or inhaled.
In summary, alpha decay is a nuclear process that reduces the size and charge of a nucleus by emitting a helium nucleus, helping heavy elements transition toward a more stable configuration.